Method and apparatus for regulating the transmission ratio of a continuously variable transmission

Abstract

A method and apparatus for regulating the transmission ratio of a continuously variable transmission. A set point value for adjusting the transmission ratio can be changed as a function of the operating parameters of a power train that includes the transmission. The set point value is composed of an initial control value and a regulating value. The initial control value depends on at least two operating parameters of the transmission. The set point value is updated to take into account changes that occur during operation of the transmission.

What is claimed is:  
     
       1. A method for regulating the transmission ratio of a continuously variable transmission for motor vehicles, to take into account changes in transmission operation over time, including changes caused by wear of transmission parts, said method comprising the steps of: 
       a. providing a preliminary transmission ratio control value as a function of at least two transmission operating parameters;  
       b. providing a set point transmission ratio value for the transmission as a function of operating parameters of a power train, wherein the set point value is composed of the preliminary transmission ratio control value and a correction value;  
       c. deriving the correction value by comparing a measured transmission ratio with the set point transmission ratio value of said transmission; and  
       d. adjusting the preliminary transmission ratio control value as a function of at least two transmission operating parameters based upon the correction value, to account for changes that occur during transmission operation over time.  
     
     
       2. A method in accordance with  claim 1 , wherein the at least two transmission operating parameters include the drive torque and the transmission ratio of the transmission. 
     
     
       3. A method in accordance with  claim 1 , wherein the preliminary control value is a function of a transmission rotational speed. 
     
     
       4. A method in accordance with  claim 1 , including the step of detecting the rate of change of the set point value. 
     
     
       5. A method in accordance with  claim 1 , including the step of generating a display when a change in the preliminary control value exceeds a predetermined limit value. 
     
     
       6. A method in accordance with  claim 1 , including the steps of: 
       a. providing preliminary transmission ratio control values as a characteristic control data field as a function of transmission operating parameters;  
       b. adjusting characteristic control data field values as a function of changes arising over time as a result of operation of the transmission.  
     
     
       7. A method in accordance with  claim 1 , including the step of detecting changes in transmission behavior when there are changes in the set point value.